Question 1hardmultiple choice
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Question 1,167 of 1,052
hardmultiple choiceObjective-mapped
CCNA Practice Question: A network administrator is troubleshooting…
This 200-301 practice question tests your understanding of 200-301 exam topics. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Exhibit
Router# show running-config | section interface GigabitEthernet0/1 interface GigabitEthernet0/1 ip address 192.168.10.1 255.255.255.0 ip access-group OUTBOUND_FILTER out duplex auto speed auto ! Router# show running-config | section ip access-list extended OUTBOUND_FILTER ip access-list extended OUTBOUND_FILTER permit tcp 192.168.10.0 0.0.0.255 host 10.10.10.10 established permit icmp 192.168.10.0 0.0.0.255 host 10.10.10.10 echo-request deny ip any any
A network administrator is troubleshooting connectivity from the 192.168.10.0/24 subnet to the server at 10.10.10.10. Users report that they can reach the server initially, but after a few minutes, connectivity drops and only returns after the interface is cleared. The administrator reviews the router's running configuration and ACL configuration. What is the most likely cause of the intermittent connectivity loss?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Remove the 'established' keyword from the ACL to allow initial TCP connections.
The ACL 'OUTBOUND_FILTER' is applied outbound on the interface facing the 192.168.10.0/24 subnet. The first line permits TCP traffic only if it has the 'established' flag set (i.e., it is part of an established session). However, the initial TCP SYN packet from the client does not have the ACK or RST flag set, so it is denied. The ICMP echo-request is explicitly permitted, but the echo-reply is not, causing ICMP to also fail after the first exchange. The correct solution is to remove the 'established' keyword or add a permit statement for initial TCP connections.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Remove the 'established' keyword from the ACL to allow initial TCP connections.
Why this is correct
The 'established' keyword only permits TCP packets with the ACK or RST bit set, which are responses to established sessions. The initial SYN packet does not have these bits, so it is denied. Removing 'established' allows the TCP three-way handshake to complete.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
CIDR notation defines the prefix length.
- ✗
Apply the ACL inbound on the interface instead of outbound.
Why it's wrong here
Changing the direction would affect traffic differently, but the core issue is the 'established' keyword blocking initial SYN packets. Inbound application would not solve the problem; it would simply filter traffic before routing.
- ✗
Add a permit statement for UDP traffic to allow DNS resolution.
- ✗
Change the wildcard mask to 0.0.0.255 to match the subnet more accurately.
Why it's wrong here
The wildcard mask 0.0.0.255 is already correct for matching the 192.168.10.0/24 subnet. Changing it would either broaden or narrow the match, but it would not resolve the 'established' keyword issue.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓Remove the 'established' keyword from the ACL to allow initial TCP connections.Correct answer▾
Why this is correct
The 'established' keyword only permits TCP packets with the ACK or RST bit set, which are responses to established sessions. The initial SYN packet does not have these bits, so it is denied. Removing 'established' allows the TCP three-way handshake to complete.
✗Apply the ACL inbound on the interface instead of outbound.Wrong answer — click to see why▾
Why this is wrong here
The direction does not change the fact that the 'established' keyword only permits packets with ACK/RST flags, which excludes the initial SYN.
✗Add a permit statement for UDP traffic to allow DNS resolution.Wrong answer — click to see why▾
Why this is wrong here
The problem is specifically with TCP connections and ICMP echo-replies, not DNS or UDP.
✗Change the wildcard mask to 0.0.0.255 to match the subnet more accurately.Wrong answer — click to see why▾
Why this is wrong here
The wildcard mask is already appropriate; the problem lies in the 'established' keyword.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Trap categories for this question
Keyword trap
Changing the direction would affect traffic differently, but the core issue is the 'established' keyword blocking initial SYN packets. Inbound application would not solve the problem; it would simply filter traffic before routing.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
- CIDR notation defines the prefix length.
- Block size helps identify subnet boundaries.
- Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
- The required host count determines the smallest suitable subnet.
TExam Day Tips
- Write the block size before choosing the subnet.
- Check whether the question asks for hosts, subnets or a specific address range.
- Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
How this comes up in practice
A security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
What to study next
Got this wrong? Here's your next step.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 200-301 subnetting questions on CIDR, address ranges, and subnet selection.
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FAQ
Questions learners often ask
What does this 200-301 question test?
CIDR notation defines the prefix length.
What is the correct answer to this question?
The correct answer is: Remove the 'established' keyword from the ACL to allow initial TCP connections. — The ACL 'OUTBOUND_FILTER' is applied outbound on the interface facing the 192.168.10.0/24 subnet. The first line permits TCP traffic only if it has the 'established' flag set (i.e., it is part of an established session). However, the initial TCP SYN packet from the client does not have the ACK or RST flag set, so it is denied. The ICMP echo-request is explicitly permitted, but the echo-reply is not, causing ICMP to also fail after the first exchange. The correct solution is to remove the 'established' keyword or add a permit statement for initial TCP connections.
What should I do if I get this 200-301 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 200-301 subnetting questions on CIDR, address ranges, and subnet selection.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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